sem_timedwait(3) [freebsd man page]

SEM_TIMEDWAIT(3)					   BSD Library Functions Manual 					  SEM_TIMEDWAIT(3)

NAME

     sem_timedwait -- lock a semaphore

LIBRARY

     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

     #include <semaphore.h>

     int
     sem_timedwait(sem_t *sem, const struct timespec *abs_timeout);

DESCRIPTION

     The sem_timedwait() function locks the semaphore referenced by sem, as in the sem_wait(3) function.  However, if the semaphore cannot be
     locked without waiting for another process or thread to unlock the semaphore by performing a sem_post(3) function, this wait will be termi-
     nated when the specified timeout expires.

     The timeout will expire when the absolute time specified by abs_timeout passes, as measured by the clock on which timeouts are based (that
     is, when the value of that clock equals or exceeds abs_timeout), or if the absolute time specified by abs_timeout has already been passed at
     the time of the call.

     Note that the timeout is based on the CLOCK_REALTIME clock.

     The validity of the abs_timeout is not checked if the semaphore can be locked immediately.

RETURN VALUES

     The sem_timedwait() function returns zero if the calling process successfully performed the semaphore lock operation on the semaphore desig-
     nated by sem.  If the call was unsuccessful, the state of the semaphore is unchanged, and the function returns a value of -1 and sets the
     global variable errno to indicate the error.

ERRORS

     The sem_timedwait() function will fail if:

     [EINVAL]		The sem argument does not refer to a valid semaphore, or the process or thread would have blocked, and the abs_timeout
			parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.

     [ETIMEDOUT]	The semaphore could not be locked before the specified timeout expired.

     [EINTR]		A signal interrupted this function.

SEE ALSO

     sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS

     The sem_timedwait() function conforms to IEEE Std 1003.1-2004 (``POSIX.1'').

HISTORY

     The function first appeared in FreeBSD 5.0.

BSD
								   March 3, 2008							       BSD

Check Out this Related Man Page

sem_wait(3)						     Library Functions Manual						       sem_wait(3)

NAME

       sem_wait, sem_trywait - Performs (or conditionally performs) a semaphore lock (P1003.1b)

LIBRARY

       Realtime Library (librt.so, librt.a)

SYNOPSIS

       #include <semaphore.h>

       int sem_wait (
       sem_t *sem);

       int sem_trywait (
       sem_t *sem);

PARAMETERS

       sem	 Specifies a pointer to the semaphore to be locked.

DESCRIPTION

       The sem_wait function locks the semaphore referenced by sem by performing a semaphore lock operation on it. If the semaphore value is zero,
       the sem_wait function blocks until it either locks the semaphore or is interrupted by a signal.

       The sem_trywait function locks a semaphore only if the semaphore is currently not locked.  If the semaphore value is zero, the  sem_trywait
       function returns without locking the semaphore.

       These  functions  help ensure that the resource associated with the semaphore cannot be accessed by other processes.  The semaphore remains
       locked until the process unlocks it with a call to the sem_post function.

       Use the sem_wait function instead of the sem_trywait function if the process should wait for access to the semaphore.

RETURN VALUES

       If the sem_wait or sem_trywait function returns successfully, a value of 0 (zero) is returned and the function executes the semaphore  lock
       operation.

       On  an unsuccessful call, a value of -1 is returned and errno is set to indicate that an error occurred. The state of the semaphore remains
       unchanged.

ERRORS

       The sem_wait and sem_trywait functions fail under the following conditions:

       [EAGAIN]       The semaphore was already locked and cannot be locked by the sem_trywait operation (sem_trywait only).

       [EINTR]	      A signal interrupted this function.

       [EINVAL]       The sem argument does not refer to a valid semaphore.

RELATED INFORMATION

       Functions: sem_post(3)

       Guide to Realtime Programming delim off

																       sem_wait(3)

Linux and UNIX Man Pages

sem_timedwait(3) [freebsd man page]

Check Out this Related Man Page